Near field communications (NFC) devices are becoming increasingly popular in sectors such as banking, as they permit rapid exchange of data over a short range (less than 10 cm), which can be used to facilitate making small value payments, for example.
NFC devices such as readers and tags transmit data by modulating a carrier having a frequency of around 13.56 MHz with a signal carrying the data to be transmitted. The modulated signal is received by a compatible NFC device such as a tag or reader having a receiver which demodulates the received signal to recover the transmitted data.
A problem with NFC communications is that the carrier in the signal received by an NFC device typically has a much greater amplitude than the data signal. This means that the NFC receiver must have a large dynamic range in order to have a high enough signal to noise ratio to permit successful demodulation of the received signal. For the same reason a clock of the receiver which provides a clock signal for demodulating the received signal must have very low phase noise. Such clocks are typically very complex, require a large area of silicon (in IC implementations), and have high current consumption.